1. Field of the Invention
The present invention relates to molecular weight-enlarged ligands for catalysts and their use for the asymmetric, homogeneous hydrogenation of double bonds.
2. Discussion of the Background
Catalytically active species for the asymmetric, homogeneous hydrogenation of double bonds are extremely advantageous for the industrial synthesis of organic substances. This is particularly the case due to their improved recyclability, which helps keep manufacturing costs low for synthetically produced products.
Molecular weight-enlarged catalysts for homogeneous enantioselective hydrogenation are known in the literature. J. Am. Chem. Soc. (1998), 120, 9481 et seq. addresses the problem of producing soluble molecular weight enlargements, inter alia, for hydrogenation catalysts. Wandrey et al have also reported the use of a molecular weight-enlarged hydrogenation catalyst in a membrane reactor (Angew. Chem. (1990), 102, 445 et seq.). U.S. Pat. No. 5,777,062 describes homogeneously soluble polymer-enlarged ligands for hydrogenation catalysts. The monomeric ligands are bound in this case to the polymer backbone via urethane or urea linkers.
The catalysts described above have problems, for example, in that it is difficult to separate the catalysts from the product with regard to the membrane used, and the catalysts become inactivated over the course of the reaction. These and other problems associated with the catalysts described above have not been adequately been resolved to date, and thus there is still a requirement for novel catalyst systems which make it possible to perform continuous processes catalytically.
Accordingly, one object of the present invention is to provide a homogenous soluble hydrogenation catalyst that is readily separable from the product of the hydrogenation.
Another object of the present invention is to provide a molecular weight-enlarged ligand for preparing such a catalyst.
Another object of the present invention is to provide a method for preparing such ligands and catalysts.
Another object of the invention is to provide a method for the asymmetric, homogenous hydrogenation of unsaturated compounds using such catalysts.
These and other objects have been achieved by the present invention, the first embodiment of which provides a molecular weight-enlarged, homogeneously soluble ligand, which includes:
an average molecular weight of at least 1000 g/mol;
a molecular weight-enlarging polymer;
optionally, a polymer linker; and
at least one homochiral active center;
wherein the active center is bound to the molecular weight-enlarging polymer through the polymer linker or is bound directly to the molecular weight-enlarging polymer; and
wherein the active center is selected from the group including compounds having the formulas in the following table, and combinations thereof:
wherein a line extending from said formulas of said active center represents a bond of a binding site both for the molecular weight enlarging polymer or for the optional polymer linker;
wherein the polymer linker is selected from the group including compounds of the formulae a)-g):
wherein
R is H, (C1-C8) alkyl, (C6-C18) aryl, (C7-C19) aralkyl, or ((C1-C8) alkyl)1-3-(C6-C18) aryl;
X is (C6-C18) arylene, (C1-C8) alkylene, (C1-C8) alkenylene, ((C1-C8) alkyl)1-3-(C6-C18) arylene, or (C7-C19) aralkylene;
Z is C(xe2x95x90O)Oxe2x80x94, C(O)NHxe2x80x94, C(xe2x95x90O)xe2x80x94, NR, O, CHR, CH2, Cxe2x95x90S, S, or PR, Z being bound directly to the molecular weight enlarging polymer;
W is C(xe2x95x90O)Oxe2x80x94, C(xe2x95x90O)NHxe2x80x94, C(xe2x95x90O)xe2x80x94, NR, O, CHR, CH2, Cxe2x95x90S, S, or PR, Z being bound directly to the active center.
Another embodiment of the present invention provides a catalyst, that includes at least one of the above-noted ligands and one or more metals or metal ions selected from the group including Ru, Rh, Ir, Pd, Ni, Pt, Co, ions thereof, and mixtures thereof.
Another embodiment of the present invention provides a process for the production of a ligand, which includes a step selected from the group including (a)-(c):
(a) binding a homochiral active center to a monomer directly or through a linker to provide a modified monomer, and polymerizing the modified monomer in the presence of one or more unmodified monomers;
(b) binding a homochiral active center to a polymer, either directly or through a linker; and
(c) carrying out either of steps (a) or (c) and further polymerizing the resulting polymer with one or more additional polymers, wherein the one or more additional polymers optionally includes one or more homochiral active centers.
Another embodiment of the present invention provides a process for producing one or more enantiomerically enriched organic compounds, which includes:
performing a reaction on a starting material that includes at least one non-chiral site to convert the non-chiral site into a chiral site;
wherein the reaction is performed in the presence of a catalyst for the reaction, the catalyst including at least one of the above-noted molecular weight-enlarged ligands.